So, I picked up a stock 03 WRX a few months ago that I am just using as a daily driver. The car runs fine, but it has a CEL light that had been on for a while, according to the previous owner. I finally got the time to investigate and get the code pulled and it read "Bank 1 Lean"... I didn't catch the actual code number. It has turned off for a while and come back on at least once since I've owned it. I've read a few things about this on other forums, but it's hard to find info on stock cars, because most people are throwing this code because of mods. The most interesting thing I found was a guy throwing this code because of a leak, and he said his turbo sounded like a stuck pig when spooling up. ...mine makes a noise I might compare to a stuck pig as well, but only under load. So, I'm think this might be a leak, but if there are other suggestions, I'm open.
If it is a leak, how should I go about finding it and fixing it?